Bit error rate testing may be performed on existing radios, i.e., determining how well a particular communication waveform is performing. More specifically, the bit error rate test may allow a user to benchmark the radio across various levels of signals that are being received relative to the noise, providing the user with a better understanding of how well the particular waveform is performing.
To perform the bit error rate test, additional components, such as signal combiners, directional couplers and attenuators, are typically added in front of the radio receiver. Furthermore, these additional components must be compensated for with respect to their impact to the measurement. Compensation methods may include calibration of additional insertion loss and non-uniform frequency response compared to the nominal state of the radio. Upon completion of the bit error rate test, the additional components must be removed to return the radio receiver back to working condition. Not only is this process cumbersome, but this process also changes the characteristics of the signal that is being measured due to the additional components.
However, such an approach reduces signal power due to conservation of energy. For example, with a power combiner, because the primary signal and the secondary signal are being summed together, a half-power loss may be realized. Similarly, with a directional coupler, a loss may also be realized during the combining (or summation) process.
Radio receivers are typically implemented by using wideband analog-to-digital converters (ADCs). These wideband ADCs may have a broad frequency response covering more than one Nyquist zone. In these instances, an anti-aliasing filter is used to only select a particular portion of the incoming signal to be converted into a digital representation for waveform processing.